Taking steps to improve patient safety and reducing adverse drug events (ADEs) is a crucial component of health care quality. ADES are known to be common and preventable in the hospital setting. However, despite the fact that most medical care is given in the ambulatory setting, relatively little is known about identifying, tracking, and preventing ADEs in this setting. There are many reasons for this gap, but perhaps the most critical is that it is challenging to identify outpatient events because of unobserved settings and poor documentation. However, as electronic medical records become increasingly common in the ambulatory setting, one of their benefits is that they will make it much easier to detect outpatient ADEs. Furthermore, computerization of prescribing represents a powerful tool for preventing ADEs. We propose to study the impact of electronic medical records and computerized prescribing in a diverse array of clinic settings associated with Partners HealthCare System and the Regenstrief Institute/Indiana University. This collaboration will bring together research groups with substantial experience in ADE detection and monitoring and outpatient computerized decision support. This study has three primary goals. First, we seek to develop improved methods for ADE detection by the use of an automated ADE monitor. This monitor will search the electronic medical record as well as the clinical information system for triggers that are highly likely to represent ADES. In this manner, the monitor Fill facilitate improved identification of ADEs, and allow tracking and analysis for prevention. Second, we seek to study the impact of electronic prescribing on preventable ADE rates in the outpatient setting by examining the impact of a basic electronic prescribing system (that includes default dosing and drug-allergy checking) on preventable ADEs, as compared to a paper-based prescribing system. Third, we will study the additional benefits of more advanced decision support, such as drug-laboratory checking and renal dosing, that aids in the prescribing process. We plan to disseminate the knowledge we gain in terms of both ADE monitoring and prevention, and in terms of potential cost savings, in order to encourage other institutions to implement these types of systems.